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Subject: Re: [PATCH v3] SUNRPC/cache: Fix unsafe traverse caused double-free
 in cache_purge
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Bruce Fields <bfields@fieldses.org>, Neil Brown <neilb@suse.de>,
        Sasha Levin <sashal@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
References: <4568a7cf87f110b8e59fda6f53fda34c550ab403.1586108200.git.wuyihao@linux.alibaba.com>
 <e0dd0339-a15e-814d-ac5a-5f51bc15d73c@linux.alibaba.com>
 <0308EB8A-A8B7-412C-8F93-A444DE47CB1D@oracle.com>
From:   Yihao Wu <wuyihao@linux.alibaba.com>
Message-ID: <25dcf75e-65b1-b6e8-1fe5-81a193ed4189@linux.alibaba.com>
Date:   Mon, 6 Apr 2020 02:31:41 +0800
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>> net/sunrpc/cache.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
>> index af0ddd28b081..b445874e8e2f 100644
>> --- a/net/sunrpc/cache.c
>> +++ b/net/sunrpc/cache.c
>> @@ -541,7 +541,9 @@ void cache_purge(struct cache_detail *detail)
>> 	dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
>> 	for (i = 0; i < detail->hash_size; i++) {
>> 		head = &detail->hash_table[i];
>> -		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
> 
> If review/testing shows you need to respin this patch, I note that "tmp" is
> now unused and should be removed. I've pulled v3 into my testing branch and
> made that minor change. Thanks!
> 
> 
>> +		while (!hlist_empty(head)) {
>> +			ch = hlist_entry(head->first, struct cache_head,
>> +					 cache_list);
>> 			sunrpc_begin_cache_remove_entry(ch, detail);
>> 			spin_unlock(&detail->hash_lock);
>> 			sunrpc_end_cache_remove_entry(ch, detail);
>> -- 
>> 2.20.1.2432.ga663e714
> 
> --
> Chuck Lever
> 
> 

Thanks a lot, Chuck!

If it needs further changes by me, I'll fix the unused 'tmp' along with them.

BTW, if you and Neil think it's proper to add Signed-off-by Neil too later,
please do, since the bug fix owes to Neil's idea :-)

Yihao Wu